China and Britain should strengthen communication and cooperation as two major powers against the backdrop of foundational changes in the world arena and jointly build a "golden era" of China-UK ties, President Xi Jinping said on Tuesday.

Xi, also general secretary of the Communist Party of China Central Committee, made the remark in a congratulatory message to the 10th UK-China Leadership Forum.

Since the forum was first held in 2007, political parties and politicians have exchanged views on issues of common concern through the forum.

It has played a positive role in developing China-UK relations, Xi said in his message. The opening ceremony of this year's forum in Beijing was on Tuesday, with some 50 representatives from both countries in attendance.

Xi said the forum should see its 10th gathering as an opportunity to inject new momentum into the comprehensive strategic partnership as China and Britain confront the 21st century and make a greater contribution to world peace and prosperity.

British Prime Minister Theresa May, who leads the Conservative Party, said in a congratulatory message that this year is of crucial importance in UK-China relations. The forum helped bring politicians of both countries together for extensive discussions on development, bilateral ties and international issues. It has played a unique role in enhancing political trust and building long-term friendship between leaders of both countries, she said.

Song Tao, head of the International Department of the CPC Central Committee, said during the opening session that China and the United Kingdom are becoming closer partners shouldering more global responsibility with great potential for pragmatic bilateral cooperation.

Peter Mandelson, president of Great Britain-China Centre, which co-hosted the forum, said he believes in the future of China-UK relations in the post-Brexit era.

He said the UK has a very strong commitment to globalization and to a rule-based multilateral trading system that "has brought so many economic benefits such as raised living standards of many countries across the globe, not only our own".

"We see today that the multilateral trading system is coming under considerable pressure from the United States. ... Mr Trump is taking unilateral measures against China," he said. "We in Europe, including Britain, cannot support that."